6. Attachments
Most self-propelled and trailed forage harvesters have a pick-up cylinder used to lift a previously cut and wilted crops. Attachments for harvesting maize and whole-crop cereals for silage can also be used on many forage harvesters.
Maize headers One type (Plate 15.7) consists of a series of dividers which guide individual rows of the crop to rotary cutters where the stems are sheared off and passed by an auger to the feed rolls. Another design (Plate 15.6) can be used to cut along or across the rows. It has smaller crop guides which direct the crop to large rotary cutters where the stems are severed and carried by the cutters to the feed rolls. A kernel processor or corn cracker (Figure 15.3) is used to break up the ears and improve the qualitv when harvesting maize for silage. Maize headers are made for harvesting 4, 6, 8, 10 or 12 rows at a time. A 10-row maize header can clear up to five hectares in an hour. Some self-propelled harvesters have an automatic steering system with sensors on the header linked to a computer in the cab.
Plate 15.7 This self-propelled forage harvester with a 10-row maize header has rotary dividers to separate the rows being cut from those left standing. It can be automatically steered to follow the rows. (John Deere)
Whole-crop headers used to cut, chop and load green cereal crops for silage are very similar to a combine harvester cutter bar and on some machines it is possible to use a rigid combine harvester header up to 6 m wide on a self-propelled forage harvester made by the same manufacturer. Some purpose-made whole-crop headers have a hydraulic motor-driven pick-up reel, self-cleaning knife sections and a hydrostatic auger reverser used to clear heavy blockages on the cutter-bar table.
Rotary Mower Some self-propelled forage harvesters can also be used with a wide rotary mower conditioner in place of the normal pickup unit used to collect previously cut and conditioned swaths. A typical three-section 8.5 m cut rotary mower header is hydraulically folded for transport.
Power requirement
Self-propelled forage harvesters have a high power requirement. A typical high-output machine with a 4.5 m pick-up and the capacity to operate a 10-row maize header will be powered by an engine of about 450 kW (600 hp). A smaller self-propelled harvester, suitable for a 6-row maize header and a 3.5 m wide pick-up cylinder will have an engine in the 200-250 kW (270-340 hp) bracket. A trailed forage harvester with a 1.7 m pick-up cylinder needs a tractor with an engine of about 85 kW (115 hp).
Plate 15.8 An automatic knife sharpener for a chopping cylinder. The grindstone is moved along rails above the cylinder while it is rotated in reverse at slow speed to obtain keener cutting edges. (Claas)
Maintenance of forage harvesters
Lubrication points must receive daily attention during the season. Follow the lubrication schedule given in the operator's handbook. Some self-propelled harvesters have central lubrication banks with groups of conveniently placed grease points connected to the more inaccessible bearings. Gearbox oil levels and tyre pressures should be checked regularly. Belt and chain drives must be correctly tensioned.
Figure 15.4 Knife sharpening mechanism. (New Holland)
Cutting flails, used on some harvesters, must be sharp and secure. Any missing or badly damaged flails must be replaced immediately to avoid rotor vibration. Flails should always be replaced in opposite pairs to maintain correct rotor balance. Nuts and bolts, especially on components which run at high speed, must be kept tight. Keep all cutting edges sharp: blunt knives give inferior results and waste power.
Plate 15.9 Loading grass onto a silage clamp using a buckrake on a 112 kW (150 hp)
wheeled loader. (JCB)
Knife sharpening Many flywheel and cylinder chop mechanisms have a built-in knife sharpener. A grinding stone is attached to guide rails which are set parallel to the edge of the knives. The cylinder is turned slowly under power and the stone is drawn across the knives by a hydraulic ram. On some machines this procedure is controlled from the cab; on older models the stone may be moved across the guide rails by hand.
The shearbar must also be sharpened from time to time to ensure a clean cut. The clearance between the shearbar and the knives is critical. This is usually a manual adjustment but some self-propelled harvesters have a small electric motor, controlled from the cab, to adjust shear-bar clearance.
The buckrake
A buckrake consists of a number of strong steel tines about 1.4 m long, bolted to a tine bar which pivots on a frame attached to the three-point linkage. The tines are tipped to drop the load with a lever which releases a locking catch holding the tines in the transport position. The tines return to the transport position when the buckrake is lowered to the ground.
A buckrake is used by reversing the tractor along the swath with the tines lowered, until it is fully loaded. The tines are pitched (angled) slightly downwards to give a clean pick up. Too much pitch may result in soil being gathered up with the swath. The crop is deposited at the clamp by tipping the tines. Economical use of the buckrake is limited to very short hauls from field to clamp, or very small-scale production.
Although very few farmers carry grass from the field with a buckrake, a tractor-mounted model is often used to load grass on to a pit or clamp if a fork lift with a grab is not available.
Forage wagons
Swaths of wilted grass can be collected with a forage wagon, a harvesting system which lends itself to silage making on smaller farms. A pick-up cylinder at the front of a high sided wagon lifts the crop to the feeder tines and a chopping mechanism. The chopped material passes into the wagon until it is fully loaded and then this is hauled to the silage clamp or pit. The load is discharged from the back of the wagon with a moving floor conveyor after opening the rear door, usually with a hydraulic ram. Some forage wagons have a cross-conveyor at the rear which can be used for direct feeding. Forage wagon capacities vary from 10 to 70 cubic metres. A typical 30 cubic metre forage wagon has a capacity of about 20 tonnes of grass and will, depending on the number and setting of the knives, have chop lengths of between 38 and 76 mm.
Silage handling and storage
Silage may be made in pits dug in the ground, clamps or heaps, silage towers, or wrapped in plastic.
Pits and clamps. Rough terrain fork trucks, front-end loaders or buckrakes can be used to fill silage pits or build clamps. Loading and consolidating silage, especially when building an above-ground clamp, has certain dangers. Never drive close to the edge when consolidating the clamp. Wide track settings will increase the stability of the tractor. Dual rear wheels are a useful aid to safe and effective consolidation of silage.
Towers. Although expensive to install, towers make complete mechanization of silage making and feeding possible. Reinforced concrete or coated steel sheets are used to construct tower silos. Silos with diameters of up to 10 m are in common use, with heights ranging from 9-24 m.
Plate 15.10 A forage wagon picks up, chops and loads a swath in a single operation. A chain and slat floor conveyor unloads the wagon from the rear after opening the tailgate. (Claas)
A dump box or forage box, combined with a blower, is generally used to fill the tower. The dump bo Sis a large hopper on wheels with a floor conveyor to carry the material to a discharge chute at the back of the hopper. A forage box is a self-emptying trailer with high sides; it can be towed by a tractor alongside a forage harvester. The blower is a high output fan, driven by a tractor or an electric motor, which fills the tower by blowing the crop up a duct into the filling hatch.
Grass is tipped into the dump box from trailers and then fed to the blower. Forage boxes discharge the crop into the blower. Some blowers have a chopping unit to cut the material into short lengths before blowing. In any case, green material stored in tower silos must be chopped into short lengths. Long material would be extremely difficult to remove from the tower.
After filling, the tower must be sealed to keep out the air. Provision is made to prevent a build-up of pressure on hot days with an expansion valve or breather bag. Air is excluded from the tower to remove oxygen which is undesirable in the silage making process. Never enter a silage tower as soon as it has been opened; it must be left open to allow oxygen in before anyone is permitted to go inside the tower.
The green material is chopped before it is blown into the tower to make mechanical unloading possible. This can be with a top or bottom unloader. Top unloaders have a series of digging teeth on an endless chain which cut and carry the silage to a blower unit at the centre of the unloader. A chute from the blower throws the silage through an opening in the side of the tower into a duct. From here, it falls to ground level where a conveyor can take the silage to the livestock. The cutting mechanism moves round on top of the silage; it has its pivot and electric motor drive at the centre of the unloader. As the level of silage falls, the unloader is lowered. It is supported from the top of the tower by chains attached to the roof.
A bottom unloader also has a cutting mechanism and conveyor. It is placed in an opening at the base of the tower. The silage gradually moves downwards as the tower is emptied. The unloader can be withdrawn from the tower for maintenance or repairs.
Plastic bags. Silage can be made by sealing the forage in plastic bags. Earlier methods involved placing the bale in a large black plastic bag or continuous plastic tube and sealing the ends to exclude the air for the fermentation process. This is a useful system for small-scale silage making, especially if half-size bales are made with a conventional baler.
Plate 15.11 This bale wrapper is suitable for round bales up to 1.3 m diameter or square bales up to 1.8 m long with sides to a maximum of 0.8 m. The bale is turned in various directions by the platform belts while it is wrapped with several layers of plastic film. (Overum)
Bale Wrappers.
These machines are used to wrap bales of green material for silage with an airtight plastic film. Bale wrappers may either be trailed or mounted. The bale to be wrapped is placed on two rollers which are mounted on a turntable either with a squeeze loader which is an integral part of the wrapper or with a separate tractor loader. The wrapping cycle is started by attaching the stretch film plastic to the bale. A combination of rotating and turning the bale results in it being covered with a complete bandage of plastic film. The number of layers applied and the amount of overlap of each layer of film can be adjusted.
Plate 15.12 A bale handler attachment for a tractor loader. Hydraulically operated rollers gently grip the wrapped bale while it is lifted and transported. (Landmec)
Once wrapping is completed, the bales can be left in the field until it is convenient to haul them to the farmyard. The bales can be transported with a tractor loader equipped with a squeeze grab or similar attachment which lifts and transports the bale without damaging the plastic.
Safety check
When using a tractor to consolidate a silage clamp keep away from the edges. Use dual wheels if possible. Ensure that the clamp is made properly with the sides well supported. It should have guard rails or edge markers along each side.
Consolidating a silage clamp is not a suitable job for an inexperienced driver.